Catalytic polymerization of unsaturated esters



Patented June 1946 CATALYTiC POLYMERIZATION OF UNSA'IURA'IIEID ESTERS David E. Adelson, Berkeley, Calif., Robert P. Ruh, Columbus, Ohio, and Harold F. Gray, Jr., Berkeley, Calii.,fassignors to Shell Development Company, San Francisco, Calii., a corporation of Delaware No Drawing. Application June 14, 1943, Serial No. 490,949

9 Claims. 1

This invention relates to a process for the.

catalytic polymerization of unsaturated esters.

More particularly, the invention pertains to polymerization of allyl esters and related compounds, the polymerization being efiected catalytically by the presence of a new class of polymerization catalysts consisting of certain metal salts.-

Unsaturated esters of the type of allyl acetate, obtainable from a monocarboxylic acid which is, devoid of any polymerizable unsaturated group and an unsaturated alcohol having an oleflnic linkage between two carbon atoms one of which is directly linked to a saturated carbon atom having a hydroxyl group linked directly thereto, are compounds which may be termed difiicultly polymerizable substances. While the action of heat, light or peroxidic substances has been used toobtain polymers from unsaturated esters of this type, none effects a rapid polymerization of the compounds and each of such catalysts is accompanied with certain disadvantages which are overcome by the present invention.

It is an object of the present invention to provide a method of polymerizing allyl acetate and related compounds.

Another object is to provide a process for obtaining polymers of unsaturated esters of the type of allyl acetate by employing as catalytic agent therefor a class of metal salts.

A further object-is to provide a class of new polymerization catalysts.

These and other objects will be. apparent from the description of the invention given hereinafter.

We have now discovered that allyl acetate and related compounds are catalytically polymerized when heated n the presence of a normal salt of an alkaline-earth metal. By a normal salt, reference is made to those salts which are devoid of peroxidic oxygen in the acid portion ofthe salt as well as being neutral salts, i. e. acid salts are excluded. Thus the present invention does not employ, as catalyst, compounds which are the saltsmay be either of organic or inorganicearth acids. Representative salts include alkaline metal inorganic salts like the halides such as magnesium chloride, calcium chloride, barium chloride, beryllium bromide, barium fluoride,

strontiumiodide, calcium fluoride, radium chloride, barium bromide, strontium chloride-etc; alkaline earth metal sulfates such as calcium sulfate, barium sulfate, etc.; alkaline earth metal carbonates'such as beryllium carbonate, radium carbonate, calcium carbonatmbarium carbonate,

strontium carbonate, etc alkal.ine earth metal phosphates such as calcium phosphate, barium phosphate, magnesium phosphate, beryllium phosphate, etc.; .alkalineearth metal nitrates such as calcium nitrate, strontium nitrate, barium nitrate, etc; alkaline earth metal sulfites such calcium sulfite, barium sulflte, etc.; alkaline earth metal cyanides such as magnesium cyanide,

known to the art as persalts, such as perborates,

strontium cyanide, barium cyanide, etcgzfaswell as double salts like Cas(PO4) 301 or Cas(Pp4)3F. Salts of organic acids also catalyze the polymerization reaction such as calcium acetate, barium acetate, strontium propionate, magnesium trichloracetate, calcium palmitate, magnesium stearate, barium oleate, calcium phthalate, beryllium acetate, radium formate, calcium levulinate, barium butyrate, strontium chloracetate, and like salts. The anhydrous salts are employed, 1. e. they are devoid of water of crystallization.

The sulfates, halides -and carbonates-form a preferred group, and, of the halides the chlorides and bromides are, particularly suited. The salts of barium, which are very active, make it the most preferred of the alkaline earth metals, although strontium salts also. possess a preferred activity. In general, the activity increases in the direction of increasing atomic weight of the metals.

A number activity by heating allyl acetate, a diflicultly polymerizable ester, in their presence. The monomeric allyl acetate was substantially pure and anhydrous and to separate quantities were added an anhydrous normal salt of an alkaline earth metal as indicated in the table below in an amount of about 0.5%. The esters in the presence of the salts were refluxed or boiled at normal pressure in a vessel fitted with a reflux condenser and the course of the polymerization was followed by observation of the refractive index taken from time to time after starting the heating. Therefractive index of the polymer, which was polyallyl acetate, is considerably higher than that of the monomer so that an increase of refractive index indicates thatpolymerization-is occurring. A blank to which no salt was added was similarly of salts were tested for catalytic (An20/DX10 ferred reactants are included such compounds as allyl formate, allyl acetate. allyl propionate, allyl isobutyrate, beta-methylallyl acetate, betachlorallyl acetate, beta-ethylallyl formate, beta- 5 phenylallyl acetate, beta-methoxyallyl acetate, for the indicated time from start. beta-chloromethylallyl acetate, allyl benzoate,

Table Hours Blank Mgou CaCl SrCO' BaF B801 mayo Ba(OAc) G2 8 64 e6 16 79 as 9% 115 11s.... 16 17s.... 24 182 198.... 202 ms 225 29 is 290.111 55' III: 12:; 31L.-- 195 388 145 111 a fig 3 Z39 504.... 159 203 0.117 0.121 cm 0.860 0.3 4 0.623 0.6 0 0441' m also shown.

The compounds polymerized according to the process of the invention are unsaturated estersof a monocarboxylic acid and the esters contain a single olefinic bond. Although the salts catalyze polymerization of any polymerizable unsat- The superior catalytic activity of the salts of metals of increasing atomic weight is urated compound, the esters employed are those of monocarboxylic acids devoid of any polymerpromoting group such as esters of acrylic acid, crotonic acid, cinnamic acid, etc. The esters are derived from a mono-unsaturated alcohol having an olefinic linkage between two carbon atoms one of which contains at least one hydrogen atom attached thereto and one of which is linked directly to a saturated carbon atom containing the hydroxyl group linked directly thereto. Preferably the ester is derived from a mono-unsaturated alcohol containing a vinylidene group directly linked to a saturated carbon atom to which is linked the hydroxyl group. Unsaturated esters of aromatic acids such as benzoic acid, toluic acid, and the like, are included within the purview of the invention since the lack of saturation of the carbon atoms in the aromatic ring of such compounds is responsible for no polymerizable unsaturated groups therein because of the well-known peculiarities of aromatic nuclei. The esters of saturated mo'nocarboxylic acids constitute a preferred group, and, while esters of simple saturated acids are particularly preferred, also included are those esters of satu rated aliphatic acids wherein one or more hydrogen atoms have been substituted by a halogen atom, a hydroxyl group, an alkoxy group, an. aryloxy group and like groups. Among the prebeta-methylallyl propionate, allyl toluate, allyl salicylate, allyl glycolate, allyl methoxyacetate, beta-methylallyl chloracetate, allyl beta-chloro propionate, allyl lactate, allyl naphthenate, betamethylallyl chlorobenzoate,- allyl alpha-hydroxyisobutyrate, allyl acetylglycolate, allyl stearate, allyl levulinate, beta-methylallyl butyrate, alphamethylallyl acetate, alpha-phenylallyl acetate, allyl ethoxyformate, beta-methylallyl phenoxyformate, allyl naphthoate, allyl ester of hydrogenated abietic acid, and the like;

The compounds of the preferred group may be represented by the general formula,

R1 R: O 4 I II on,- -o-oc wherein R1, R2 and R3 represent hydrogen atoms, halogen atoms or hydrocarbon radicals and R4 represents a hydrogen atom or an organic radical devoid of a polymerizable unsaturated group, such as an alkyl group, an aryl group, an allcyclic group, an aralkyl group, an alkoxy group, an aryloxy group, and the like.

Less preferred esters include compounds like crotyl acetate, crotyl propionate, crotyl benzoate, 2-hexenyl acetate, z-pentenyl formate, 2-isopentenyl chloracetate, methyl isobutenyl carbinyl butyrate, and similar types of ester.

The polmerization is effected by heating the unsaturated ester under anhydrous conditions in the presence of or in contact with the catalyst salts at a temperature of 50 C. to C. with the ester in the liquid phase. With unsaturated esters of sufilciently low melting point so that they are liquid under the reaction conditions, the ester is polymerized in the process per se. The use of higher esters requires the use of an inert solvent in order to have the reaction mixture liquid under the conditions prevailing in efi'ecting the polymerization. For this purpose solvents such as saturated esters like ethyl acetate, isopropyl acetate, butyl acetate, etc.; hydrocarbons like benzene, toluene, hexane, octanes, etc.; ethers like dioxane, dibutyl ether, beta-dichlorosolvents, or diluents' where possible since they complicate the recovery problem in. obtaining the polymer and decrease the rate of the polymerization reactions. It is preferred to employ as'reactant an unsaturated ester which is liquid under the reaction conditions as is realized with lower esters or esters of lower unsaturated alcohols. These preferred reactants contain not more than seven carbon atoms in the unsaturated-ester;

6 While the salts employed as catalyst dissolve to a greater or lesser extent in th'e'reaction material, they are normally soluble in only minute amounts so that the reaction mixture is contacted with the catalyst as a crystalline substance. For this reason it is preferable to utilize the salt in the finely divided or comminuted state.

Amounts of catalyst from a few hundredths of 1% to 5% or more are efiective in reactions.

The normal salts of alkaline earth metals have advantages in polymerizing the unsaturated esters not realized with known peroxidic catalysts such as benzoyl peroxide, one of the most commonly used materials for this purpose. The salts are cheap and this is true of the most active of them. the barium salts. Since they are essentially insoluble in the reaction mixture, the polymer ob tained is not contaminated with undesirable materials such as enzoic acid as when benzoyl peroxide is utilized. Furthen' upon completion of the polymerization operation, the catalyst is illtered from the reaction mixture and can be used again in the process. In view of these advantages it is evident that catalyst cost according to the present invention is reduced to a minimum.

In executing the process of the invention the unsaturated ester to which has been added an amount of catalyst is heated to between 50 C. and 150 C., and the heating continued until the desired degree of polymerization has occurred. The polymers of the unsaturated esters are linear polymers which are generally soluble in the monomeric material. the reactant has been converted to polymer. as may be determined by observation of increase 'of the unsatucatalyzing the After to or more of perature and monomeric ester is fed into the cycling system while inaterial is withdrawn therefrom, the withdrawn portion being a mixture of polymer and monomer from which the monomer is' recovered for return to the cycling System;

1 The polymers prepared according to the m vention have application as plasticizers and sorteners for various materials. Further, their-sol bility in various substances makes the polymer 0 esters useful intermediates in the synthesis of polymeric alcohols which may be prepared by hydrolysis orisaponification of the polymers.

We claim as our invention: j

1. A process for the production oia polyallyl acetate which consists of heating allyl acetate in the liquid phase under anhydrous and nonoxidizing conditions in the presence oi a barium chloride for a time sufilcient to effect appreciable polymerization of the allyl acetate.

2. A process for the production of polyallyl Y acetate which consists of'boiling allyl acetate at atmospheric pressure under anhydrous and nonthe refractive index, the heating is discontinued The filtered material is then subjected to.

whereby the polymerization is efiected by refluxing the material in the presence of the catalyst. The presence or absence of oxygen appears to have no significant efiect on the rate of the polymerization reaction when the catalysts of the present invention are employed. In some cases it is desirable to add intermittently fresh catalyst to the reaction material durin the course of the heating rather than adding the entire amount at the start.

Another method of effecting the reaction which is adapted for continuous production of polymer with the catalyst salts is to pass the liquid reactant material through a bed of the salt. In adapting this procedure to continuous operation of the catalyst maintained at the desired temearth metal salt of a non-peroxy acid, said heatoxidizing conditions in thepresence of a barium carbonate -for a time sufficient to efiect appreciable polymerization of the'allyl acetate.

3. A process for the production of polyallyl acetate which consists of boiling allyl acetate at atmospheric pressure under anhydrous and nonoxidizing conditions in the presence of strontium carbonate for a time suflicient to effect appreciablepolymerization of the allyl acetate.

4. A process for the production of a polymer of a mono-olefinic ester of a monocarboxylic acid and a monohydric alcohol havingan oleflnic linkage between two aliphatic carbon atoms one or which has at least one hydrogen atom linked directly thereto and the other of which is linked directly to a saturated carbon atom having the hydroxyl group linked directly thereto, which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and halogen, which consists of heating said ester under anhydrous and non-oxidizin conditions'at a temperature of from 50 C. to C. in the presence of a neutral alkaline-earth metal. salt of a non-perox'y acid, said heatin being continued for a time sufllcient to effect appreciable polymerization of said ester.

5. A process for the production of a polymer of a mono-oleflnic'ester of a monocarboxylic acid and a mon'ohydric alcohol having a vinylidine group linked directly to a saturated carbon atom to which is directly linked the hydroxyl group,

which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and halogen, which consists of heating said ester under anhydrous and non-oxidizing conditions at a temperature of from 50 C. to 150 C. in the presence of a neutral alkaline ing being continued for a time suflicient to effect appreciable polymerization of said ester.

6. A process for the production of a polymer of a mono-olefinic ester of a monocarboxylic acid and a monohydric alcohol having a vinylidene group directly linked to a saturated carbon atom to which is directly linked the hydroxyl group, which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and halogen, which consist of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of from 50 C. to 150 C. in the presence of a neutral alkaline earth metal halide, said heatsalt of a non-peroxy acid, said heating being con tinued for a time suflicient to effect appreciable polymerization of said ester.

8. A process forlthe production of a polymer of an allyl ester of saturated monocarboxylic acid which ester contains not more than 7 carbon atoms, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of from 50 C. to 150 8 C. in the presence of a neutral alkaline earth metal halide, said heating being continued for a time sufficient to efl'ect appreciable polymerization of said ester.

9. A process for the production of a polymer of an allyl ester or a saturated monocarboxylic acid which ester contains not more than Icar- 'bon atoms, which consists of heating said ester in liquid phase under anhydrous and non-oxidiz ing conditions at a temperature from 50 C to 150 C. in the presence of a barium dihalide for a time sufficient to effect appreciable polymerization of said ester.

' DAVID E. ADELSON.

HAROLD F. GRAY, JR. ROBERT P. .RUH. 

